You can use DVD or USB, but USB is faster. Check you can actually boot from the media you create. I'd keep the multiboot box ticked as recommended. I do that and the recovery drive boots fine.

When you clean install Windows 10 and it updates to the latest version, I recommend archiving that clean install image in case you need to restore that in the event of serious system problems....

You can clean up these partitions if you are sure of what you are doing but is it worth the risk of making your PC unbootable for the small amount of space saved?